library improvements

Sources/AudioTeeCore/Utils/AudioTeeLogger.swift

@@ -0,0 +1,44 @@
+import Foundation
+
+// MARK: - Logging protocol
+
+/// Protocol that library consumers implement to receive log output.
+/// The library never writes to stderr directly — it calls through this.
+public protocol AudioTeeLogger {
+  func debug(_ message: String, context: [String: String]?)
+  func info(_ message: String, context: [String: String]?)
+  func error(_ message: String, context: [String: String]?)
+
+  /// Called for structured lifecycle messages (metadata, stream_start, stream_stop).
+  /// Default implementation is a no-op — pure library consumers get metadata
+  /// via AudioOutputHandler instead.
+  func writeMessage<T: Codable>(_ type: MessageType, data: T?)
+}
+
+// MARK: - Defaults
+
+extension AudioTeeLogger {
+  /// Library consumers typically don't need structured message output;
+  /// they receive metadata via the AudioOutputHandler protocol instead.
+  public func writeMessage<T: Codable>(_ type: MessageType, data: T?) {}
+
+  /// Convenience overloads so callers can omit context when it's nil.
+  public func debug(_ message: String) { debug(message, context: nil) }
+  public func info(_ message: String) { info(message, context: nil) }
+  public func error(_ message: String) { error(message, context: nil) }
+}
+
+// MARK: - Global logging configuration
+
+/// Global logger instance. Defaults to StderrJSONLogger (CLI behavior).
+/// Library consumers can replace this before calling any AudioTeeCore API.
+///
+///     // Silence all logging:
+///     AudioTeeLogging.logger = NullLogger()
+///
+///     // Custom logging:
+///     AudioTeeLogging.logger = MyOSLogLogger()
+///
+public enum AudioTeeLogging {
+  nonisolated(unsafe) public static var logger: AudioTeeLogger = StderrJSONLogger()
+}

Sources/AudioTeeCore/Utils/Logger.swift

@@ -1,7 +1,10 @@
 import Foundation
 
-public class Logger {
-  nonisolated(unsafe) private static let dateFormatter: ISO8601DateFormatter = {
+/// Default logger implementation that writes JSON messages to stderr.
+/// This is the CLI-appropriate logger; library consumers can replace it
+/// via AudioTeeLogging.logger.
+public class StderrJSONLogger: AudioTeeLogger {
+  private let dateFormatter: ISO8601DateFormatter = {
     let formatter = ISO8601DateFormatter()
     formatter.formatOptions = [
       .withInternetDateTime,
@@ -10,17 +13,22 @@ public class Logger {
     return formatter
   }()
 
-  private static let jsonEncoder: JSONEncoder = {
+  private let jsonEncoder: JSONEncoder = {
     let encoder = JSONEncoder()
-    encoder.dateEncodingStrategy = .custom { date, encoder in
-      var container = encoder.singleValueContainer()
-      try container.encode(dateFormatter.string(from: date))
-    }
     return encoder
   }()
 
-  // Write any message with the unified envelope
-  public static func writeMessage<T: Codable>(_ type: MessageType, data: T? = nil) {
+  public init() {
+    // Configured in init because stored property initializers can't
+    // reference other instance properties (self.dateFormatter).
+    jsonEncoder.dateEncodingStrategy = .custom { [dateFormatter] date, encoder in
+      var container = encoder.singleValueContainer()
+      try container.encode(dateFormatter.string(from: date))
+    }
+  }
+
+  // Write any message with the unified envelope to stderr
+  public func writeMessage<T: Codable>(_ type: MessageType, data: T?) {
     let message = Message(type: type, data: data)
     do {
       let jsonData = try jsonEncoder.encode(message)
@@ -32,17 +40,17 @@ public class Logger {
   }
 
   // Convenience methods for different message types
-  public static func info(_ message: String, context: [String: String]? = nil) {
+  public func info(_ message: String, context: [String: String]? = nil) {
     let logData = LogData(message: message, context: context)
     writeMessage(.info, data: logData)
   }
 
-  public static func error(_ message: String, context: [String: String]? = nil) {
+  public func error(_ message: String, context: [String: String]? = nil) {
     let logData = LogData(message: message, context: context)
     writeMessage(.error, data: logData)
   }
 
-  public static func debug(_ message: String, context: [String: String]? = nil) {
+  public func debug(_ message: String, context: [String: String]? = nil) {
     let logData = LogData(message: message, context: context)
     writeMessage(.debug, data: logData)
   }

Sources/AudioTeeCore/Utils/Utils.swift

@@ -15,7 +15,7 @@ func isAudioDeviceValid(_ deviceID: AudioObjectID) -> Bool {
 
   let valid = status == kAudioHardwareNoError && isAlive == 1
 
-  Logger.debug(
+  AudioTeeLogging.logger.debug(
     "Checked device validity",
     context: [
       "device_id": String(deviceID),
@@ -63,7 +63,7 @@ func translatePIDsToProcessObjects(_ pids: [Int32]) throws -> [AudioObjectID] {
 
     if status == kAudioHardwareNoError && processObject != kAudioObjectUnknown {
       processObjects.append(processObject)
-      Logger.debug(
+      AudioTeeLogging.logger.debug(
         "Translated PID to process object",
         context: [
           "pid": String(pid),
@@ -71,7 +71,7 @@ func translatePIDsToProcessObjects(_ pids: [Int32]) throws -> [AudioObjectID] {
         ])
     } else {
       failedPIDs.append(pid)
-      Logger.debug(
+      AudioTeeLogging.logger.debug(
         "Failed to translate PID to process object",
         context: [
           "pid": String(pid),
@@ -87,11 +87,3 @@ func translatePIDsToProcessObjects(_ pids: [Int32]) throws -> [AudioObjectID] {
 
   return processObjects
 }
-
-extension String {
-  func print(to fileHandle: FileHandle) {
-    if let data = (self + "\n").data(using: .utf8) {
-      fileHandle.write(data)
-    }
-  }
-}